Valve for locomotives



Feb. 4, 1941.

w. F. KIESEL, JR 2,230,327

VALVE FOR LOCOMOTIVES Filed Dec. 50, 1938 OOOGOOOOOOOOOOOOO GOOOOOOGOQOOOOOO OOOOOOOOOOOOOOO Patented Feb. 4, 1941 UNITED STATES rarest orrice of one-third to Virginia Kiesel Rutan, Harrisburg, Pa., one-third to John S. Kiesel, Williamsport, Pa., and on e-third to William F.

Kiesel, 3rd, Stewart Manor, Long Island, N. Y.

Application. December 30, 1938, Serial No. 248,593

2 Claims.

This invention relates to valves for variable speed steam engines and more particularly to such valves for use with steam locomotives.

It is a general object of the present invention 5 to provide a novel and improved valve for variable speed steam engines.

More particularly, it is an object of the invention to provide, in a valve for steam locomotives, separate ports for admission and exhaust of steam for cooperation with the conventional type of movable valve element.

Another object of the invention is to restrict the area of the admission port in a variable speed engine valve so that for any length of valve travel required for smooth operation it will pass no more steam than the boiler can continuously supply.

An important feature of the invention consists in the provision of a slide valve, for locomotive steam engines, which produces earlier virtual cutoff, with the consequent reduction in steam consumption, by a throttling action resulting from reduced admission ports of such size that they permit the entrance of the full quantity of steam required 'at low speeds, but which at high speeds automatically reduce the quantity of steam delivered to the cylinder, whereby the valve does not require adjustment for early cut-off, which adjustment in the usual valve produces undesirable release and compression timing.

Another important feature of the invention consists in the provision of a steam engine valve having a set of main ports, which under normal operation are fully uncovered solely for release or exhaust of the steam, together with a set of auxiliary ports fully uncovered at each stroke of the movable valve member and operating for admission only, the auxiliary ports being sized to an area not greater than three per cent of the flue area of the locomotive, nor greater than onethird of the main port area as determined by wellknown formulas for locomotive design.

Other and further features and objects of the invention will be more apparent to those skilled in the art upon a consideration of th e panying drawing and following specification, wherein is disclosed a single exemplary embodiment of the invention, with the understanding that such variations and changes may be made therein as fall within the scope of the appended claims, Without departing from the spirit of the invention.

In said drawing,

Figure 1 is a longitudinal section through a portion of a steam engine cylinder and through the valve and chamber therefor;

Figure 2 is a transverse section on line 22 of Figure 1, showing the arrangement of the auxiliary ports; and

Figure 3 is a transverse sectional view on a reduced scale through the cylinders, valves, and smoke box of a locomotive, looking toward the rear, and showing the forward flue sheet in elevation.

The well-known slide valve as used in most steam engines is quite satisfactory for moderate speed operation, since it can be designed and set to provide satisfactory timing of the four major events in the operation of the piston of the en- 1 gine. Admission or opening of the valve can be arranged just prior to dead center to start the flow of live steam sufliciently early to have it become effective as soon as the piston starts on the return stroke and cut-off of the steam can be arranged to provide the desired expansion and either maximum economy, maximum power or some optimum condition. Release can be set a predetermined amount prior to opposite dead center and compression adjusted to the proper 2 amount to absorb the unbalanced energy of the piston and start it on its return stroke.

Unfortunately such a valve does not lend itself Well to high speed and high power operation for the four events are so correlated, because of the unitary structure of the moving part of the valve, that no one of them can be changed by a mere setting of the valve or adjustment of its stroke without changing all of them. Thus when it is desired to run at fairly high speeds and capacity, early cut-off is required and the usual valve gear designed for variable speed operation produces excessive compression caused by the change of the movable valve member position and the shortening of the stroke thereof. This causes the exhaust ports to be materially restricted and thus poor operation results.

Most engine designers have generally assumed that admission of steam into the cylinder by the valve should be as free as possible, and port areas and valve openings are designed and adjusted for this and every eiiort is made to obtain a relatively sharp cut-off indication on the indicator card. With this type of valve, the setting of the valve gear for high speed operation, with early cut-off,

shortens the travel, which has the effect of making the exhaust closure earlier on the return stroke thereby materially reducing the port-opening to the exhaust.

The present invention is based on the knowledge that it is important to get rid of the steam in the cylinder with the least amount of back pressure and it is therefore assumed that the problem is not so much one of introducing steam into the cylinder but mainly bf exhausting it as freely as possible under all valve settings. With this premise, the present invention, while relating particularly to locomotives, but not so restricted, has been made with the thought uppermost in mind that freedom of exhaust should take precedence over freedom of admission.

Locomotives of conventional design, and most of them use a single piston valve for each cylinder, develop excessive back pressure and compression in the main steam cylinders when running at high speed with the reverse gear hooked up for very early cut-off. Locomotive valves and gear must be designed for a late maximum cut-off in order to have sufficient starting power and the change in valve piston movement necessary to advance the cut-off from, say 75% or 80% to 10% or 15% is quite considerable and the valve piston stroke is materially shortened. This results in the aforementioned excessive back pressure and compression, causing a bucking action in the operation of the engine at the end of each return stroke. This produces rough riding, hot crank pins and journals, loss of power, and excessively high cost of maintenance of the locomotive. An experienced engineer tries to improve conditions as much as possible by partially closing the main throttle to permit him to use a somewhat later cut-oil", with somewhat greater steam consumption in the endeavor to obtain a greater freedom of exhaust. Such operation is a decided help but does not permit realizing the maximum capabilities of the steam used.

In accordance with the present invention a more efiicient use of steam at high speed is achieved by automatically providing for earlier effective or virtual cut-olf without the necessity of shortening the valve stroke. This permits retaining the exhaust port areas and interval of opening at a maximum for all speeds. The effective or virtual cut-off may be said to comprise the resultant of the real cut-off and the restricg I p ,v

tion in the quantity of steam supplied due to the reduced size of the admission ports. It is clear that the length of time that the restricted admission ports are opened determines the total quantity of steam delivered to the cylinder and this length of time in terms of percentage of stroke length is regulated by the real cut-off.

In order to understand the reasons underlying the novel features of the present invention, it is essential'to visualize what takes place in the cylinder of .a steam engine of the type used on high speed locomotives. One of the most serious difiiculties experienced in the operation of such engines is a substantial increase in back pressure when using steam near the maximum boiler capacity. This back pressure is influenced by the size and shape of the exhaust nozzle which induces the draft in the boiler fiues. Considerable sacrifice must be made in order to obtain maximum draft to increase the boiler capacity since its size is restricted by limitations which cannot be removed. In present day locomotives when steam is used at approximately of boiler capacity, the back pressure in the exhaust passages, and hence in the cylinder, is as much as 22 to 25 pounds gauge, while for 40% boiler capacity it is only from 2 /2 to 3 pounds gauge. Fora given train requiring the locomotive to use 100% of boiler capacity for a speed of 100 miles per hour, the high back pressure produces a serious increase in compression if the exhaust ports are closed too early. With the conventional valve the exhaust ports must be closed early as a concomitant to the achievement of early cut-off which is essential for operation within the boiler capacity, Early cut-off requires a short valve stroke which produces excessive compression.

To achieve a reduction in the compression a longer valve stroke is essential and here the present invention steps in and permit-s any desired length of valve stroke without unduly affecting virtual cut-off. The result is obtained by making use of an entirely independent set of admission ports controlled by the same movable valve member as the main set of ports which function solely for exhaust. The'se supplementary admission ports are designed to pass a maximum amount of steam as nearly as possible equal to the maximum steaming capacity of the boiler and are opened to their full extent regardless of the actual cut-ofi" adjustment of the valve which permits making the valve stroke to suit the speed and cylinder back pressure.

Considering now the same train assumed be-' fore, it will be seen that it is now possible'to set the valve to give the desired compression pressure and in so doing the actual cut-off is late, but the virtual cut-off, because of the throttling action of the restricted admission ports, is early at the high speed. If the speed is reduced to 60 miles per hour only about 40% boiler capacity is required and the valves can be set to operate more nearly as the conventional valves giving as early cut-off as desired and relatively early compression which can cause no serious trouble now because the back pressure is reduced. Between 60 and 100 miles per hour the valve stroke is gradually lengthened to give sufiicient compression, predicated on back pressure, to properly counteract the unbalanced portion of reciprocating weights.

In the accompanying drawing the invention is shown as applied to the inside admission type of 5 piston valve now almost universally used by locomotive builders and railroads, although the in vention is equally as applicable to the usual 'D- slide valve and to the various balanced versions The valve chamber has reduced cylindrical 'ends I5, closed by heads 11, one of which is arranged for the passage of valve stem I8 through a suitable packing gland I9. Although it is possible to have these ends themselves provide the working surfaces for the movable portion of the valve,

it is preferred to fit them with sleeves orbushings 20 of identical construction, so that a description of but one is necessary. Each'sleeve is arranged for a press fit within the end portion N5 of the valve chamber and has an inner cylindrical working surface 2! of uniform diameter between 22 and 23, this distance being equivalent to the stroke plus substantially the length of the cooperating or head portion of the movable valve member. Beyond 23, increased. diameter 24 prevails, and this .portion is perforated by a series of ports 25 leading into the circumferential chamber 26 connected to the exhaust passage, not

shown.

The main portion of the sleeve is provided with a plurality of circumferen-ti-ally disposed main or exhaust ports 23, the outer edges 29 of which are preferably in a plane at right angles to the valve stem I8 so that they are all opened simultaneously. These main ports have such a combined area as to provide the freest possible flow of exhaust steam in keeping with the other characteristics of the locomotive, and well-known formulas are used in their design.

The ports 28 open into a circumferential chamber 30 merging with the passage 12 leading to the cylinder.

A second circumferentially disposed set of ports hereafter referred to as admission ports is arranged in each valve sleeve inwardly of the ports 28. These admission ports 3| are arranged with their inner edges preferably lying in a plane at right angles to the valve stem and are each of the same length longitudinally of the sleeve so that each opens and closes along with all of the others under the action of the movable portion of the valve.

The combined area of the admission ports in one sleeve is considerably less than that of the exhaust ports, being preferably not more than one-third of the total area of these exhaust ports.

The movable portion of the valve comprises a central barrel 33 having enlarged heads or pistons 34 each fitted with the customary packing rings 35 and 36 closely engaging the walls of the sleeves 2B. These packing rings serve to control the flow of steam through the various ports, completely shutting oif these ports when they are covered thereby.

In the present construction the overall length of the packing rings from 40 to 4| is such that they may cover, simultaneously, ports 28 and 3| and provide also the customary exhaust and steam laps as desired by the designer for the proper operation of the engine. Because of the greater distance between the outer edges of the exhaust ports and the inner edges of the admission ports, a somewhat longer valve head is required to close them both.

For normal operation the valve travel is designed to carry the edge 48 at least to and preferably somewhat beyond the inner edges 29' of the ports 28, insuring full opening for the exhaust ports under all conditions of operation, thus contributing materially to the smooth operation of the locomotive.

For all normal settings of the valve gear, the admission ports are fully uncovered once per stroke by the edge AI of the packing rings, but except under unusual settings of the valve the exhaust ports are not uncovered by valve piston edge M on the admission operation of the valve. It will be clear that the admission ports feed into the same chamber 30 as do the exhaust ports.

In order to appreciate the operation of the present invention, it should be noted that in locomotive design work it is often convenient to measure the boiler capacity for evaporation in terms of flue area, the total net cross-sectional area of all the fines in the boiler, or as a summation of the visible areas of the flue ends 42 in Figure 3, less the areas of superheater pipes therein. In a well designed locomotive, a maximumv of about 10,000 pounds .of water per square foot of net flue area can be evaporated per hour, and this "flue area thus forms a convenient basis for determining port sizes in connection with the valves and cylinders. In the present invention the total area of the admission ports in on end of the valve is proportioned to pass steam only up to approximately the maximum boiler steaming capacity and is restricted to not more than three per cent of the flue area, whereas the total area of the exhaust ports in one end of the valve will be considerably greater than this as determined by the usual formulas.

In operation, it will be seen that at slow speeds the restricted port admission areas produce no substantial throttling of the steam since the main piston moves ahead slowly enough to permit steam to enter as rapidly as the cylinder volume behind the piston incerases and thus the pressure in the cylinder will be close to that in the steam-chest until actual cut-01f by the valve. This permits operation at heavy loads at the longest possible cut-off for which the Valve is designed, and With full power from full steam flow.

As the speed of the locomotive increases, however, the piston movement becomes more rapid so that the volume behind it increases more rapidly than steam can flow into this volume through the restricted area of the still fully opened admission ports without substantial loss of pressure in the cylinder. Thus a progressively decreasing quantity of steam per revolution is provided to the cylinder as the speed increases. This has substantially the same efiect as earlier cutoff since it permits greater expansion of the steam in the cylinder and a full realization of the work available from it. By properly sizing the admission ports commensurate with the maximum boiler capacity, there is achieved the virtual equivalent of any desired early cut-01f of the older constructions without the necessity of so setting the valve that admission, release and compression are not timed for most effective operation.

The sizing of the ports. as previously mentioned, such as less than three per cent of the net "flue area or somewhat less than one-third of the exhaust port areas as determined from standard formulas, is found essential for ordinary locomotive operation, producing the desired throttling of steam during admission to obtain the equivalent of the most efi'ective early outoiT when the locomotive is traveling at high speed.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent is:

1. A piston valve for a steam engine comprising a ported bushing and a reciprocating piston having a head provided with spaced cut-off and release edges, said bushing having two sets of ports therein spaced apart in the direction of piston movement but occupying an overall length less than the distance between said edges, one of said sets of ports being of normal size and fully uncovered once per stroke by said release edge, the other set of ports being for admission and being fully uncovered once per stroke by said admission edge, said admission ports being of such reduced size as to throttle the steam to provide earlier virtual cut-ofi with increased engine speeds, said second set of ports being subject to such valve piston overtravel that release and compression can be adjusted without changing the virtual cut-ofi. v

2. A piston valve for a steam engine comprising a steam chamber having a bushing in each end thereof and a live steam space therebetween,

two sets of ports in each said bushing leading to the corresponding end of a steam engine cylinder, a slidable valve member in said chamber having a central body portion and piston-like ends closely fitting said bushings and cooperating with the ports therein to control the flow of live and exhaust steam therethrough, said ports being a1- lotted respectively to live and exhaust steam and adapted to be independently and always'fully area can be adjusted to vary compression with- 10 out changing the virtual cut-off.

WILLIAM F. KIESEL, JR. 

